Complement

Abstract

The complement system was initially viewed as an arm of innate immune defenses against invading pathogens by tagging them for elimination by professional phagocytes or by direct killing through pore formation. The association between hereditary or acquired complement deficiencies and invasive meningococcal infection is well established. Over the past few decades, the diverse roles of complement, including bridging innate and adaptive immunity, disposal of apoptotic cells and immune complexes, tissue regeneration, organogenesis, and metabolism, have been elucidated. Elucidation of the intracellular complement system in T cells, macrophages, and even nonimmune cells is an exciting new area of investigation. Novel therapeutics that block complement activation are actively being developed. The current review provides an overview of how complement combats infections and its increasingly appreciated roles in maintenance of physiology of the host and in the pathogenesis of noninfectious conditions.

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